Biological macromolecules such as recombinant monoclonal antibodies and other proteins are used in a wide array of diagnostic and therapeutic areas. Especially monoclonal antibodies are now widely used in various severe diseases like cancer or rheumatoid arthritis. Commonly, these complex biological molecules are produced by fermentation processes with bacteria, yeasts or mammalian cells. Traditionally, the microbial or mammalian cells are removed from the fermentation broth by centrifugation or filtration and thereafter the cell free supernatant is further purified from fermentation related impurities by various methods like filtration, precipitation and chromatography.
Main impurities from the fermentation processes, beside the media components, are the residual amounts of nucleic acids (host cell DNA (HCDNA) and RNA) and Host Cell Proteins (HCP) from the cells that produce the biological macromolecule. For therapeutic purposes the acceptable concentrations of Host Cell DNA (HCDNA) or Host Cell Protein in the final drug substance are very low in order to reduce adverse effects and guarantee patient safety. Recent improvements in fermentation technology have led to higher cell densities in the production bioreactors, which increase the levels of HCP and HCDNA in the cell free supernatant placing higher demands on the purification process.
Effective and cheap methods to remove large amounts of HCDNA and HCP from cell culture supernatants are therefore highly desirable.
O'Brien, W. D., et al. (J. Acoust. Soc. Am. 52 (1972) 1251-1255) report the ultrasonic investigation of aqueous solutions of deoxyribose nucleic acid. Vorlickova, M., et al. (Nucl. Acids Res. 27 (1999) 581-586) report the dimerization of the guanine-adenine repeat strands of DNA. Acid precipitation of mammalian cell fermentation broth is reported by Lydersen et al. (Lydersen, B. K., et al., Ann. N.Y. Acad. Sci. 745 (1994) 222-231). A method of isolating biomacromolecules using low pH and divalent cations is reported in WO 2008/127305. In EP 1 561 756 and EP 1 380 589 methods for purifying protein are reported.